The Sony ILCE-7RII also offers – apart from plenty other new features – an improved autofocus in comparison to its predecessor and its sister models. It should even make the more expensive, heavier and bigger Sony LA-EA4 obsolete when using A-mount lenses with SAM- and SSM-drive and claims to be at the same AF-speed of E-mount lenses with the LAEA-3 adapter. This is something I wanted to double-check…
I already wrote about the bunch of improvements of the Sony ILCE-7RII habe ich bereits in my report on the Sony alpha Festival. The improved autofocus is the most obvious one because Sony is using the latest generation of processors and sensor to als improve the AF performance with adapted lenses and this not only ohne using a e.g. Metabones-adaptor of the last generation for Canon lenses but also when using the Sony LA-EA3 to adapt A-Mount lenses having a SAM- or SSM-drive. Lenses with rod driven focus system still require the Sony LA-EA4, this is something I can say right away.
The two pictures above show the visual differences of Sony LA-EA3 (left) and Sony LA-EA4 (right). Where the LA-EA3 only performs an electrical and mount adaptation, the LA-EA4 provides a fully independent autofocus Modul of the Sony SLT-65 including the SLT-mirror element (as shown in the left picture above) and a motor for the rod driven mechanical AF lenses. This makes the LA-EA4 not only bigger and adds 55 grams to the weight but also turns it into an accessory that consumes the already limited battery power of the mirrorless Sony cameras. The little hitch of the A-mount rod drive is shown on the upper right picture next to the SONY label of the right adaptor and it is also shown the the LA-EA3 on the left is missing this coupler.
How the adaptors work
The LA-EA4 has its own PDAF (Phase Detection Auto Fokus) – modul and is therefore completely independent from the AF system of the camera. The LA-EA3 does not offer any AF functionality and leaves AF control to the camera. The PDAF-modul of the LA-EA4 is taken from the SLT-65 and has 15 AF sensors of which 3 are cross-type sensors. I am sorry to disappoint those of you who now think that the LA-EA3 would be the better choice for all Sony mirrorless cameras. Up to now, only the contrast-base AF of the attached cameras worked with the LA-EA3 which means 25 contrast AF points with the hybrid-AF of the ILCE-6000 – the 179 OnSensorPhaseDetect-AF (OSPDAF) sensor remain unused. The same is valid for the hybrid-AF of the ILCE-7 with 25 contrast and 117 OSPDAF sensor elements. The problem ist the principle of the constrast-AF which measures the contrast on contours in the image and adjusts the focus until the grading between bright and dark has reached its shortest distance meaning its sharpest increase. This method of focussing is a lot more slower than the procedure with phase detection although phase detect focussing is older. Phase detection measures the distance to the object to focus on by triangulation where two sensors look though the same lens and uses the created stereo image. Based on this the second measurement at the latest clarifies in which direction and how far the focus needs to be adjusted. Just for completeness and even it has nothing to do with how the adapters work some quick words on the hybrid AF which is available on all three used cameras. The hybrid AF uses specially arranged pixels on the sensor which take over the functionality of the phase detection AF. The switch between phase detect (PD) and contrast AF works seamlessly when in standard setting. In good light conditions the more precise contrast AF is used and in bad light conditions the faster PD-AF is taking over. I am not covering the different configuration options of the three cameras here – but this would be something for a separate post.
Comparing focus speed of LA-EA3 and LA-EA4
With the introduction of the ILCE-7RII – Sony wrote it in the description – the LA-EA3 is now supposed to take full advantage of the hybrid AF of the camera, which means in the case of the ILCE-7RII that the LA-EA3 can focus SAM- and SSM-lenses using the 399 OSPDAF-sensors and this with almost the same speed like with any other E-mount lens.
But bevor showing how this feature looks like I would like to show how the Sony SAL 70-400 F4-5.6 G SSM behaves on the ILCE-6000 and the ILCE-7 with both LA-EA3 and LA-EA4. I mounted both adaptors on all three camera and focussed the Sony SAL 70-400 F4-5.6 G SSM three times on close distance and a far object in variation. I used a HDMI gabbing device to record the EVF image to show the focussing speed of both adapters in a video. The measuring of focussing time was not done by a highly sophisticated device. Instead I simply counted the video frames between the moment when the blur started to change which is the moment when the shutter button was pressed and the black screen shown in the EVF when the picture was taken. The count of frames was divided by 25 frames per second and the result is the time needed for focussing – the shutter button was pushed down all the time.
LA-EA3 and LA-EA4 on ILCE-6000
The video shows that the LA-EA3 has some difficulties to set focus with the SAL 70-400 G mounted on the ILCE-6000 for both distances, close and far. None of the measurements was below 5 seconds and the second measuring at far distance even took 7.32 seconds! The interesting part is: Sometimes it looks like the focus point was reached and the picture could have been taken, but suddenly the focus drives off and slowly oscillates back to the (assumed) same focus point again.
Completely different the behavior of the LA-EA4 on the ILCE-6000: The longest focussing takes 0.56 seconds, the shortest only 0.32 seconds – good values, ignoring the inaccuracy of the measuring method. Since the values are not really readable in the video because they are only shown for a short moment I have summarized them in a little table::
|A||5.52 s||0.40 s|
|B||6.72 s||0.56 s|
|C||5.20 s||0.32 s|
|D||7.32 s||0.56 s|
|E||5.24 s||0.32 s|
|F||5.92 s||0.32 s|
LA-EA3 and LA-EA4 on ILCE-7
Both adaptors behave very similar on the ILCE-7. It is remarkable though that the ILCE-7 is a bit faster in focussing with the LA-EA3 than the ILCE-6000 which is quite surprising, because the ILCE-6000 is advertised by Sony to be the camera with the fastest AF. The combination of LA-EA4 and ILCE-7 takes almost twice the time for focussing than the ILCE-6000 which surprises me even more, because I thought the AF Modul of the adapter does all the work. Why this? This question can only be answered by a Sony engineer. My best guess: In the end it is all a matter of software and which parts of the BionzX processor takes over the AF work. This is the table with all the measurements on the ILCE-7::
|A||5.04 s||0.72 s|
|B||5.72 s||1.12 s|
|C||4.96 s||0.60 s|
|D||6.28 s||0.88 s|
|E||4.96 s||0.68 s|
|F||6.32 s||0.60 s|
LA-EA3 and LA-EA4 on ILCE-7RII
Obviously Sony as not exaggerated with: „You can make use of the advantages of PhaseDetection-AF when using the lens adaptor LA-EA3 with A-Mount lenses (SAM/SSM).“ . In total there are many innovations to point out regarding AF-speed on the ILCE-7RII, e.g. that the performance of the hybrid-AF has increased by 40% – something which I did not verify yet. This is all thanks to the BSI-sensor, the back-lit CMOS-sensor which also speeds up the data transmission by factor 3.5. This also shows in the fact, that the ILCE-7RII is the first camera of the 7-series which has the AF-A mode. Asking a Sony representativ during the alpha Festival in Berlin I got the confirming answer that this was not possible with the sensors used up to now because they are to slow.
Since the measurements are not displayed long enough in the video for all 12 measurements I summarized them in a table again, which show an enormous reduction of focussing time when using the LA-EA3 and that these times are now very close to the times of the LA-EA4 – now offering all advantages of the hybrid-AF like for example the greater image sensor coverage with AF sensors.
|A||0.68 s||0.64 s|
|B||0.60 s||0.52 s|
|C||0.80 s||0.40 s|
|D||0.68 s||0.40 s|
|E||1.00 s||0.56 s|
|F||0.68 s||0.48 s|
To make a long story short: The LA-EA4 does not make any sense any more on the ILCE-7RII, except you want to use lenses with rod driven focus. On all other mirrorless cameras the LA-EA4 offers the big advantage of PD-AF, where the LA-EA3 can only use the slower contrast AF – even when you must accept the disadvantages of the LA-EA4 which are the smaller coverage of the image sensor with AF-sensors and that it „only“ has the AF-modul of the SLT-65.